JP5158394B1 - Ground improvement device - Google Patents

Abstract

The present invention provides a ground improvement method and a ground improvement device which prevent liquefaction by desaturation and solidification of the ground by injecting a silica solution mixed with fine bubbles into the ground.
By injecting a liquid mixed with fine bubbles through an injection pipe around and / or directly under the existing structure 73, the ground is desaturated to prevent liquefaction. A shielding wall 74 is formed so as to surround a certain region by injecting a binder into the ground. The ground is desaturated by injecting into the ground in the shielding wall 74 a liquid whose gas dissolved amount is increased by mixing gas into the liquid under pressure.
[Selection] Figure 18

Description

The present invention relates to a ground improvement device for preventing ground liquefaction by injecting a chemical solution such as silica grout mixed with fine bubbles (microbubbles) and desaturating the ground, in which bubbles are mixed under pressure. By injecting the chemical liquid into the ground, the chemical liquid can be widely and evenly injected while maintaining a high concentration of dissolved gas in the ground.

  Moreover, by this, fine bubbles are permanently present in the ground, and a high quality improvement effect is obtained. Furthermore, the permeability to fine-grained soil is high, and the liquefaction prevention effect can be sustained for a long time.

  The liquefaction countermeasure work that prevents the liquefaction immediately below the existing structure and the surrounding ground by injecting a chemical solution such as silica grout is to increase the concentration of the chemical solution and to narrow the injection interval in order to make the effect sufficient. Thus, there is a problem in economical efficiency because it is necessary to increase the injection amount of the chemical solution.

  In addition, it is generally difficult to sufficiently cover the ground improvement area due to the fact that the chemical solution is difficult to penetrate widely into the ground and the drilling hole for inserting the injection tube into the ground directly under the structure is difficult. There were also construction issues.

  In addition, construction in places that are in contact with people, such as residential land, has environmental effects such as groundwater contamination due to chemical injection, impacts on the house due to ground deformation, and economic problems. Most of the countermeasures for liquefaction have not been carried out, and for this reason, development of more economical and safer liquefaction countermeasures was urgently required.

  By the way, in recent years, methods for preventing liquefaction have been proposed by injecting water in which fine bubbles (microbubbles) are mixed into the ground, or once pumping up groundwater to desaturate the ground.

  Furthermore, a bubble mixing method (micro bubble water mixing method) has been proposed in which a large number of ultrafine bubble-dissolved water having a diameter of 10 μm to 100 μm is injected into the ground to increase the desaturation of the ground.

  This method absorbs the excess pore water pressure generated during liquefaction by contraction of ultrafine bubbles mixed between the soil particles, thereby suppressing the increase in excess pore water pressure, thereby maintaining the meshing between the soil particles. It is intended to improve the forming strength.

JP 2003-205228 A JP 2005-169286 A JP 2009-121066 A JP 2010-248698 A

  The above-described bubble mixing method is expected as a new liquefaction countermeasure method, but still has some problems to be solved as described below.

  (1) Since water has a large surface tension, even if it mixes air while stirring in water or attempts to atomize air mixed in through a filter material, it does not become fine bubbles of 100 μm or less, but moves to the groundwater surface. It is difficult to form unsaturated ground because it disappears.

  In the conventional technique of injecting water containing air bubbles into the ground, air bubbles are generated in a tank on the ground and injected into the ground using a pump, so liquid containing air bubbles is injected into the ground. At the same time as it is released, it becomes an atmospheric pressure state, so that the diameter of micronized bubbles increases and the permeability decreases, and large bubbles rapidly rise in the groundwater and burst and disappear at the groundwater surface. For this reason, it is difficult to keep the dissolved amount of air mixed in the liquid constant, so it is difficult to ensure quality.

  (2) A ground improvement method is known in which an aqueous solution containing fine bubbles (microbubbles) is generated in a tank on the ground by blowing air into the water using a bubble generator and injected into the ground. However, the fine bubbles in the tank have a particle size of 5 μm to 60 μm, which is almost equal to the particle size of the cement. Therefore, when this is injected into the ground through the injection tube, it is between the soil particles near the injection tube. Air bubbles are likely to be clogged in the gaps and gather around the injection tube. For this reason, it is difficult to form the unsaturated ground by allowing the bubbles to penetrate evenly and widely.

  This is because when the tank is pressurized and air is mixed using a bubble generator, the fine particle size of the above particle size is maintained in the tank, but when injected into the ground, the pressure is released. This is because the bubbles gather to increase the particle size, and therefore, the permeability decreases or becomes large bubbles and is easy to escape to the ground.

  Further, if the fine particles are aggregated, the unsaturated effect cannot be increased while maintaining the fine bubbles, so that the improvement effect is lowered. Furthermore, the microbubbles having the above particle diameter are dispersed in a milky white state in water, but disappear with time and become transparent.

  This is because, due to the surface tension of water, the bubble particle size is reduced and the pressure inside the bubble is increased, so that the solubility of the gas in water increases and eventually disappears. Therefore, it is difficult to maintain the unsaturated state on the ground for a long time.

  (3) When there is a groundwater flow directly under a river embankment, the injected quality will not be able to ensure and maintain the expected quality over a long period of time because the injected bubbles will flow out and diffuse out of the injection target area. In addition, there is a concern that the degree of saturation may be recovered due to the movement of bubbles due to the advection of groundwater after construction or the release to the ground, which is sufficient as a long-term liquefaction countermeasure method for earthquakes that do not know when it occurs. That's not true.

  (4) Since the bubble mixing method is based on the principle of adsorbing fine bubbles on the surface of the soil particles, an aqueous solution containing fine bubbles is generated, and this is injected through the injection tube while maintaining a pressurized state in the ground. Since the pressure must be released to generate bubbles in the ground, it is difficult to cope with the system and operation.

  That is, using a device that generates air bubbles, a liquid containing air bubbles is generated and injected through the injection tube while maintaining the pressurized state in the ground, and the pressure is released in the ground and the ground is released. The system in which air bubbles are generated to reach the unsaturated state is complicated, and it is difficult to maintain a pressurized state until the pressure is released and air bubbles are generated in the ground.

The present invention has been made to solve the above-described problems, and enables easy production of a large-volume injection material mixed with microbubbles (fine bubbles), and bubbles are mixed under pressure. By injecting the chemical into the ground, it is possible to inject bubbles widely and evenly while maintaining a high concentration of dissolved gas in the ground, and fine bubbles are permanently present in the ground. It is intended to provide a ground improvement device that has a high quality improvement effect, has high permeability to fine-grained soil, and can sustain the liquefaction prevention effect of microbubbles over a long period of time. is there.

The ground improvement device of the present invention is a ground improvement device that desaturates the ground and prevents liquefaction by injecting a liquid mixed with fine bubbles through the injection pipe into and around the existing structure. A bubble generation device that mixes fine bubbles into the liquid fed through the liquid supply tube, a compressor that feeds air into the bubble generation device, and an injection tube that injects the liquid mixed with the fine bubbles into the ground, The bubble generating device has a liquid introduction path, a liquid introduction hole, and a liquid discharge path through which the liquid fed through the liquid feed pipe flows, and the liquid introduction path has a conical shape that gradually decreases in diameter in the liquid flow direction. The liquid introduction hole is formed between the liquid introduction path and the liquid discharge path, and is sent from the air compressor to the inner wall surface of the liquid introduction hole. An air discharge port for discharging air is provided .

According to the present invention, a shielding wall is formed so as to surround a certain region by injection of a binder in the ground, and a gas dissolved amount is obtained by mixing gas into the liquid under pressure in the ground in the shielding wall. It is possible to desaturate the ground by injecting at a high level, and to form a plurality of solidified bodies in the ground and to dissolve the gas by mixing gas into the liquid under pressure between the solidified bodies. The ground can also be desaturated by injecting in higher amounts .

In addition, it is suitable for ground improvement to prevent liquefaction by desaturating the ground by injecting a liquid mixed with fine bubbles around the existing structure and / or directly below the ground, especially in a certain area in the ground. A shielding wall (continuous underground wall) is formed so as to surround the liquid, and liquid can be prevented from being discharged by injecting a liquid mixed with fine bubbles into the shielding wall, and around the existing structure and / or Alternatively, it is possible to reliably and economically improve the ground immediately below the ground.

  In addition, by using a silica solution as the liquid, fine bubbles are permanently present in the ground due to the desaturation and consolidation of the ground, resulting in a high-quality ground improvement effect and permeability to fine-grained soil The liquefaction prevention effect can be sustained for a long time. In addition to the silica solution, microbubbles may be generated in a solution containing salt, acid, alkali or organic substance, electrolyte, surfactant, and water-soluble polymer material.

  By using this method, electrolyte ions accumulate at a high concentration around the microbubbles in the process of shrinking, and the action of suppressing the dissolution of the gas inside the bubbles occurs. A wide range of permeability in fine-grained soil.

  In addition, by forming a plurality of consolidated bodies (improved bodies and / or continuous walls) in the ground, it is possible not only to prevent lateral flow of the ground, but also to increase the supporting force of the ground. Can be stabilized.

  The consolidated body can be easily formed by a method such as improvement to a ground containing a large amount of a solidified material such as silica solution or cement solution. If necessary, the consolidated body can be reinforced with steel pipes or shaped steel. You may drive in the pile which consists of steel materials or RC structure. Furthermore, by repeatedly injecting fine bubbles into the ground, the fine bubbles can be widely dispersed and injected into the ground.

  In particular, the bubble generator is installed in a solution introduction pipe connected to a liquid feed pipe that is installed in a straight line in the tank or spirally along the inner wall surface of the pressurized tank and extends from the solution circulation pump to the pressurized tank. By installing a plurality of microbubbles in the direction of the pipe axis of the introduction pipe, it is possible to generate a large volume of microbubbles, thereby efficiently generating a large volume of liquid (chemical solution) mixed with microbubbles. .

  In addition, the bubble generator is also installed in the injection pipe or the liquid supply pipe laid between the pressurized tank and the injection pipe, so that microbubbles are mixed again into the microbubble mixed liquid generated in the pressurized tank. By doing so, a liquid (chemical solution) mixed with more microbubbles can be injected into the ground.

  In addition, a plurality of liquids (chemical solutions) mixed with microbubbles can be obtained by arranging injection pipes at a plurality of injection points via branch valves or electromagnetic valves, and by using an extraction device for extracting the injection pipes at each injection pipe. In addition to being able to select and inject at the same time or some of the injection points, it is possible to inject an optimal amount of liquid at each injection point and for each layer at each injection point without waste.

  In addition, by connecting multiple injection pipes to each other via a liquid supply pipe and installing a flow path switching bubble at each injection point of the liquid supply pipe, the optimum flow path for the liquid up to the injection point can be selected arbitrarily can do.

  By the way, the applicant has used the following characteristics of microbubbles (fine bubbles) for many years to eliminate the drawbacks and use an electrolyte solution as a solution, and use a solution type injection material mixed with microbubbles. The liquefaction countermeasure work according to the present invention was completed.

  After dissolving the gas in the electrolyte solution under pressure, release the pressure and create a gas supersaturation condition to generate bubbles in the water, or create a vortex by generating a water flow, and entrain the gas in the vortex When the liquid is collapsed, the permeation distance of the bubble-containing liquid is significantly increased as compared with the case where the liquid is water, the liquefaction strength is increased, and the durability of the improvement effect is also increased. In particular, it has been found that the effect is remarkable when the electrolyte is a silica solution.

  This is because when microbubbles are mixed in water, the particle size of the microbubbles is large, and microbubbles gather around the injection holes at the beginning of injection, and the bubbles have surface tension at the interface between the microbubbles and the surrounding water. It acts, the internal pressure increases, and the diameter decreases and disappears in a short time.

  On the other hand, when microbubbles are mixed in the electrolyte, the microbubbles mixed in the electrolyte are concentrated at the interface even if the internal pressure of the bubbles is high, and the concentration of the electrolyte is high. Microbubbles are hardly dissolved and microbubbles with a smaller diameter than microbubbles are generated, and the nanobubbles continue to exist without disappearing for a long time. This is probably because the injection solution with good microbubbles penetrates a wide area.

  Nanobubbles are extremely fine bubbles having a particle diameter of 1 μm or less, and have a characteristic that they exist in water for a long time. For this reason, for the purpose of preventing liquefaction, if bubbles with a particle size of 100 μm or less can be present for a long time without disappearing in water, the above-mentioned drawbacks can be prevented with a bubble mixed liquid to prevent liquefaction. We paid attention to the following functions to be applied to the ground improvement.

  (1) A bubble mixed liquid having not only microbubbles but also nanobubbles is formed.

  (2) Make sure that the period of disappearance of bubbles in the groundwater is lengthened so that it will penetrate evenly into the injection target area without disappearing during the injection time.

  (3) While microbubbles and nanobubbles may eventually disappear, let them persist permanently in the ground.

  The present inventor has made various studies in order to provide the above functions, and completed the present invention by using the following method.

  (1) Nanobubbles as well as microbubbles are efficiently generated in the ground and penetrated extensively before disappearing.

  (2) Make an insoluble shell at the bubble interface and fix the gas in the ground. Therefore, microbubbles are generated in a solution containing a silica solution, salt, acid, or alkali or organic substance as an electrolyte.

  By using this method, electrolyte ions accumulate at a high concentration around the microbubbles in the process of shrinking, and the action of suppressing the dissolution of the gas inside the bubbles occurs. Will exist. For this reason, a wide range of permeability in fine-grained soil is obtained.

  However, on the other hand, both microbubbles and nanobubbles may eventually disappear, and there is a risk of disappearance due to the groundwater flow. For this reason, bubbles are generated in an aqueous solution containing silica having a gelling function. In this way, microbubbles and nanobubbles can sufficiently permeate into the ground, and finally gelate to form a permanent unsaturated ground.

  In particular, microbubbles are extremely reactive because they generate free radicals in addition to the concentration of surface charges and the generation of nanobubbles when they disappear. For this reason, even if the silica concentration is a dilute silica concentration that does not form a gel containing all of the blended water, the silica precipitated in the blend solution forms a shell covering the surface of the bubbles, and the bubbles are stabilized or linear. It is considered that the silica is entangled with the air bubbles on the surface of the soil particles and solidifies the air bubbles.

  In the ground improvement method of the present invention, any one of the following steps (1), (2) and (3), or two steps or all three steps are used in combination.

  (1) A gas is mixed into a sealed liquid under pressure to create a supersaturated gas mixed liquid, which is injected into the ground through an injection tube to release the pressure and generate bubbles in the ground.

  (2) A gas mixture in a supersaturated state under pressure is jetted from a nozzle in water or in an injection pipe to release the pressure to generate bubbles in the ground.

  (3) The ground is desaturated by stirring, mixing, and dissolving the liquid and gas with the vortex generator and injecting them into the ground.

  In the above system, the liquid is an electrolyte solution, a silica solution, or a bubble-containing water and an electrolyte or silica-containing bubble-containing liquid. Alternatively, the liquid may contain a surfactant or a water-soluble polymer thickener.

  Thickening agent is added to the microbubble injection material, and 0.1 to 5% by weight is added, and it is not diluted with groundwater. Useful for desaturation.

  Furthermore, during the total blending of thickeners in silica-based compound aqueous solutions or colloidal solutions containing microbubbles, 0.1 to 5% amount of gel is blended for a long time and does not dilute with groundwater and penetrates a wide range. An injection material that is solidified is injected into the ground where countermeasures against liquefaction are required or ground with groundwater, and is desaturated to solidify the ground.

  Further, the thickener does not adversely affect the caking properties and caking strength of the obtained injection material, and is, for example, a water-soluble polymer thickener, specifically, for example, a polysaccharide or Examples thereof include derivatives thereof, natural gums, and water-soluble synthetic polymer substances.

  Examples of polysaccharides or derivatives thereof include alkali metal salts such as sodium carboxymethyl cellulose (cmc), hydroxyethyl cellulose, sodium starch glycolate, sodium phosphate phosphate, sodium alginate, propylene glycol alginate, sodium caseinate, and natural gums. Examples include gum arabic, alginic acid, casein, guar gum, gluten, and roast bean gum. Examples of the water-soluble synthetic polymer include polyvinyl alcohol and sodium polyacrylate.

  The compounding amount of such a thickener is the silica concentration of the aqueous solution or colloidal liquid of the silica compound, the pH value, the type of the thickener, the solidified strength of the resulting injection material mixture, The amount is such that the resulting injection material exhibits a viscosity of 2 to 40 cps, preferably 2 to 20 cps, depending on the presence or absence of groundwater and the strength of its flow. Specifically, this amount is preferably in the range of 0.1 to 5% by weight in the infusate mixture.

  Examples of the surfactant include sodium dodecyl sulfate, dodecyl trimethyl ammonium bromide, polyoxyethylene dodecyl ether and the like.

  In order to mix gas into the liquid, a swirl flow is formed while the liquid is fed under pressure, a gas is ejected into the swirl flow, and the gas is entrained in the swirl and subdivided to form a supersaturated state. Then, this is injected into the ground from the outlet of the injection tube to release the pressure to regenerate the bubbles.

  The bubble-containing solution generated by forming a swirling flow in the bubble generation device of the injection pipe is supersaturated in the injection pipe, and is discharged from the discharge port of the injection pipe into the ground, and hits the ground water in the ground and swirls. It is collapsed to regenerate the bubbles and injected into the ground.

  The present invention provides a ground improvement method and a ground improvement device capable of permeating micro bubbles in a wide range in the ground and permanently holding them.

  As the ground improvement device, liquid is fed while maintaining a large amount of air bubbles and fine particles in the injection liquid production device on the ground and maintaining fine particles in the injection pipe.

  Then, until it is injected into the ground from the discharge port of the injection tube, it is injected into the ground in a bubble mixed state so that the microbubbles do not disappear. Further, microbubbles are regenerated and injected into the ground in the injection pipe, at the spout from the injection pipe, and at the branch point from the injection liquid production apparatus to the injection pipe.

  The microbubbles injected into the ground are mixed in the silica solution so that they do not permanently disappear, so that the microbubbles are retained in the silica gel.

  In addition, a constrained state is created in the ground in advance so that the microbubble liquid injected into the ground is held in the ground while containing bubbles, and is injected into the liquid.

  Alternatively, microbubble liquid is injected into the ground once or a plurality of times to unsaturate the ground over a wide area, and then a silica solution or silica solution mixed with microbubbles (silica bubble) is injected to spread the microbubble over a wide area. Immobilize to. The micro bubble liquid and the silica bubble are repeatedly injected so that the micro bubble diffuses widely and is fixed in the ground.

  Further, the microbubble-containing liquid is constrained by being simultaneously injected from a plurality of injection holes so that the microbubble-containing liquid does not escape during the injection. Also, before injecting microbubbles by injecting from multiple outlets at the same time or by injecting from a column penetration source and injecting a large volume of infusion solution into the ground in a short time to gel in a short time It can be hardened.

  In order to allow the injection solution containing bubbles to penetrate into the ground efficiently and before the bubbles disappear, keep the vortex-induced bubbles in a predetermined pressure state and maintain the supersaturated state, while injecting the injection solution into the ground. It is preferable to use an injection device that discharges and regenerates bubbles.

  In addition, by allowing the permeation between soil particles with a large discharge amount by the columnar permeation method, it is possible to permeate a wide range in a short injection time before the bubbles disappear.

  In addition, it is possible to use a technique such as completing injection over a wide range in a short time before bubbles disappear, by simultaneously injecting from many outlets while injecting from a single outlet at a low discharge amount. desirable.

  Furthermore, the entire injection region or the injection region is divided by a chemical injection solidified body and a water blocking wall (continuous underground wall) to maintain the constrained state, and the gas mixture is injected into the supersaturated state of the injection solution. It is better to regenerate the bubbles after permeating over a wide range while maintaining the above.

  Alternatively, even if a solidified body is formed at an interval in the ground by chemical solution injection or compaction injection, and a gas mixed solution is injected during that time, the same effect as injecting into the constrained ground can be obtained. .

  Alternatively, by forming a high-strength solidified body (pile and / or shielding wall) in the injection region of silica bubbles (silica solution mixed with microbubbles), the solidified body or solidified due to the solidification effect of silica bubbles. It is possible to reduce the load at the time of the earthquake that acts on the united body.

  For this reason, a solidified body resists the big earthquake load which cannot be endured only by the ground improvement of the injection | pouring of a silica bubble, and can improve the earthquake resistance of a structure.

  In the present invention, bubbles are mixed in a pressurized airtight container or a pressure-injection pipe monitor, or bubbles are mixed in an injection liquid feeding pipe and directly injected into the ground. It is possible to control the amount of mixed bubbles, and a uniform improvement effect can be obtained. Further, since the bubbles are fed under pressure until just before the injection, the bubbles are injected in a fine state, and thus the permeability is excellent.

  Also, liquid and air are simultaneously sucked into the bubble generator (vortex generator), and the liquid and air are stirred, mixed, and dissolved in the apparatus to mix the finely divided air into the liquid and inject it into the ground. Can do.

  An example of a method of mixing bubbles in the ground tank is shown in FIGS. The above ground tank is a closed type tank that can be pressurized. A circulation pump is connected to the tank, and a device for mixing bubbles by a swirling flow is connected between the circulation pump and the pressurized tank.

  The circulation pump is connected between the pressurized tank and the bubble generator. Alternatively, as shown in FIGS. 8 (a) and 9 (a), a three-way valve is connected to the chemical supply side, the pressurized tank, and the bubble generator.

  In the injection, after supplying the chemical solution to the pressurized tank 1 in the pressurized state (P0), bubbles are generated while circulating the solution stored in the tank and injected through the injection tube.

  In FIG. 8 and FIG. 9 (a), a plurality of branch valves or bubble generation devices that also serve as branch valves are attached to the pressurized tank, and an injection pipe is connected to the tip. The branch valve is released with a pump pressure (P1) that is equal to or higher than the tank pressure (P0), and when the tank pressure is increased to a pump pressure (P1) that is equal to or higher than (P0), the branch valve is released and bubbles are introduced into the injection pipe. The mixed liquid flows.

  Therefore, the injection pressure is the actual injection pressure (P2) = pump pressure (P1) or pressure gauge pressure (apparent pressure)-tank pressure (P0), and the pressurizing pressure that increases the amount of dissolved air is the tank pressure (P0). Become.

  Further, the branch valve may be a structure in which the branch valve is simply branched, a bubble generating device, or a structure including both of them. Further, the nozzle at the tip of the injection tube may be released by the tank pressure (P0) (FIG. 5).

  In the embodiment shown in FIGS. 7 and 8, the outer injection tube is an outer injection tube provided with a double packer, and the sleeve of the outer injection tube has elasticity that expands due to the hydraulic pressure (P0) from the inner tube and opens. It has become.

  The injection tube can be an injection monitor or an outer injection tube used in the double packer method (FIG. 8) or the extractor method (FIG. 14). Liquid supply, circulation and injection construction management can be controlled by a batch construction management system.

  As shown in FIGS. 5 to 7, 9, 10, and 16, the method of mixing bubbles with the injection monitor has two or more pipelines, one of which is a pipeline that feeds liquid. Yes, the other is a pipe that feeds air, and air is mixed into the liquid by a swirling flow at the top of the injection monitor.

  In FIG. 7, the inner tube packer attached to the injection tube monitor expands at (P0) and exhibits the packer effect. After that, when the pressure rises to a certain pressure (P1), the liquid is injected into the ground. Therefore, the injection pressure is (P2) = (P1)-(P0), and the pressure for increasing the dissolved amount of air is (P0).

  The inner tube packer may be expanded by the injection pressure of the injection material, or may be expanded by sending liquid or air through another flow path.

  The bubble generating device may be provided in the pipe line to the injection inner tube (FIG. 5 (a), FIG. 7, FIG. 9 (b), FIG. 14), or may be provided in the distribution unit of the distribution device (FIG. 8). ,Ten). In addition, this monitor can be applied to the outer pipe of the double packer method or the extractor method (Figs. 7 to 16). Furthermore, by using a multiple injection system, simultaneous injection and construction management at multiple locations can be performed. It is possible (FIGS. 8 to 15).

  In addition, according to the present invention, liquid and air are simultaneously sucked by a bubble generator (vortex generator), and the liquid mixed with microbubbles is extremely efficiently obtained by stirring, mixing, and dissolving the liquid and air in the apparatus. Can be generated.

  As such a vortex generator, for example, a vortex turbo mixer (KTM) manufactured by Nikuni Corporation can be used. This device has a built-in impeller that rotates at high speed by power, and simultaneously sucks liquid and air by high-speed rotation of this impeller, and generates vortex in the device and pressurizes it. By stirring, mixing, and dissolving the liquid and air, a liquid in which microbubbles having a bubble diameter of about 10 μ are mixed can be generated extremely efficiently and in large quantities (see FIG. 17 (c)).

  Moreover, according to this apparatus, the pressurization tank (tank for melt | dissolving gas in a liquid), an agitator, a mixer, a compressor, etc. in embodiment shown in FIGS. 1-3 is not required, and also high pump capability Therefore, the injection material mixed with the microbubbles can be directly injected into the ground from the apparatus through the pressure feeding pipe without using an injection pump (see FIG. 17 (a)). Of course, it can also be incorporated in the ground improvement device shown in FIGS. 1 to 3 instead of the bubble generating device shown (see FIG. 17B).

  Although the liquid used for this construction method and this apparatus can be water, it may be diluted by the movement of groundwater as in the previous construction method. In that case, by adopting a construction method that can leave the outer pipe, such as double packer construction method or exppacker construction method, it is possible to re-inject bubbling water or bubbling silica solution when saturation rises. It is.

  This silica solution (which also contains a gelling reagent) has an improved uniaxial compressive strength and the like depending on the silica concentration, and the silica concentration can be set according to the purpose. In addition, when the improvement coefficient is permanently expected by lowering the permeability coefficient of the improved range from that of the original ground and preventing the groundwater from flowing into the improved area, a composition with a silica concentration of 4% or less is appropriate, For the purpose of preventing liquefaction and suppressing deformation, the silica concentration should be 4% or more.

  At any concentration, solution-type water glass grout (silica grout obtained by adding acid or salt to water glass), non-alkaline water glass (mixture of water glass and acid, pH is weakly alkaline to acidic value. Compared to the case of injecting only water containing bubbles by using silica grout with colloidal silica and a reactive composite silica grout (non-alkaline silica grout mixed with colloid, water glass and acid agent). As a result, the liquefaction strength increases. This is because the Poisson's ratio of the homogel is lower than that of water.

  In general chemical injection, sufficient liquefaction strength cannot be obtained unless the silica concentration is increased and the gap filling rate is sufficient. However, in the present invention, the gel becomes agar-like by reducing the silica concentration. Therefore, it can be deformed without breaking against the increase of excess pore water pressure due to earthquake, so the gas bubble adapts to the deformation of the gel and absorbs the increase of excess pore water pressure to express the seismic effect of unsaturated ground can do. In particular, the bubble-containing silica can form a gel in which the gel can be displaced.

  And since it adds to the adhesion effect of the sand particles of silica gel, even if the silica concentration is low, a high liquefaction strength can be obtained without destroying the skeleton structure of the soil particles. In addition, the unsaturated soil block can be held against the flow of groundwater by increasing the degree of unsaturation by enlarging the bubbles and increasing the degree of unsaturation and wrapping the large unsaturated soil block with a thin silica gel membrane. .

  Moreover, at the time of an earthquake, a thin gel film | membrane deform | transforms easily and internal gas compresses and can absorb a seismic load and can obtain big liquefaction strength. The silica concentration can be 0.1-40 wt%, but 0.1-4 wt% is particularly preferable. The silica solution is preferably water glass containing silica gel, silica colloid, or a mixture thereof.

  Further, the silica solution is accompanied by gelation due to the presence of an acid, and the silica gel becomes weakly alkaline to acidic due to dealkalization, thereby obtaining durability of silica.

  In addition, it is shown in Table 1 about the relationship between the silica density | concentration and fracture | rupture distortion | strain after a silica solution gelled for 28 days, and a silica density | concentration and a gel state.

  Silica gel has lower strength as the silica concentration decreases, but the fracture strain increases. Or it becomes a jelly-like gel, and the distortion increases without showing a peak indicating fracture.

  Even in such a case, if the silica concentration is such that the gel is precipitated, the adhesive force of the silica particles acts and the skeleton structure of the soil particles is maintained. Silica gel becomes a loose gel at a silica concentration of about 2% and is not capable of containing all of the water at 0.1 wt% or more, but it is effective for bonding silica particles deposited on the ground during the pouring process. Work.

  Accordingly, it is desirable to use a silica solution having a silica concentration of 0.1 wt% or more and about 40 wt% for the ground improvement method. When the silica concentration is 4 wt% or more, the strength is high, and even if bubbles are present, the liquefaction strength is determined by the silica concentration. Further, when the silica concentration is higher than 4% wt, the amount of silica to be used is reduced by increasing the degree of unsaturation, the effect of gas desaturation is increased, and an economic effect can be obtained at the same time.

  The degree of unsaturation should be 3% or more. The larger the degree of unsaturation, the less liquefaction will occur due to the formation of unsaturated ground below the groundwater surface. In order not to escape to the ground, the unsaturated soil block may be fixed under the groundwater surface with silica. Specifically, the degree of unsaturation should be within 95%.

  When the degree of unsaturation is the same, the liquefaction strength of the bubbles to which silica is added is greatly increased compared to the case of bubbles alone. Further, the liquefaction strength is greatly increased even when the silica concentration is the same as compared with the case of using only the silica solution. Further, in this case, the liquefaction strength becomes larger than the total strength of the liquefaction strength of only the silica solution and the liquefaction strength of only the bubbles, and the synergistic effect is obtained.

  For this reason, sufficient liquefaction strength can be obtained even if low-concentration silica that cannot be obtained by liquefaction countermeasures only by gelation of the silica solution is used. In this case, the concentration of the silica solution is 0.1 to 40 wt%, preferably 0.1 to 3 wt%.

  Further, the silica concentration is effective even at a thin concentration where an injection effect cannot be obtained with a grout of only a silica solution. In other words, the silica solution alone is effective even at such a thin concentration that the silica gel cannot contain the total amount of water in the compounded solution (silica concentration is 2 wt% or less). It is thought to adsorb and fix between soil particles.

  In addition, it is considered that the gelation function of silica is improved by free radicals that generate microbubbles.

  In addition, by injecting a bubble grout (water containing fine particle bubbles) in advance, a silica solution or a bubble-containing silica solution is injected into a dense region of bubbles gathered in the vicinity of the injection tube, and the periphery of the bubbles is filled with a silica solution. It can be extruded to form a bubble ground.

  In this case, prior to injecting the silica solution or the bubble-containing silica solution (silica bubble), the bubble-containing liquid may be repeatedly injected to push the bubbles over a wide area to form an unsaturated ground over a wide area.

  By doing in this way, it turned out that it is easy to form the consolidation zone by the bubble mixing silica grout in which the bubble was distributed to the whole injection | pouring object ground.

  Similarly, by injecting a silica injection solution having a high bubble content in the initial stage of injection, and then injecting a silica injection solution having a low bubble content, a silica solution having a low bubble content is higher than a silica solution having a high bubble content. Therefore, it is possible to average the unsaturated soil of the entire injection region by expanding the bubble region previously injected to the periphery.

  Further, by covering the fine bubbles with a silica dilution gel, the bubbles can be restrained to prevent the bubbles from being dispersed and diffused, and the compressibility of the bubbles can be maintained without breaking the gel. In addition, since the diluted silica containing bubbles has a function of displacing the gel or sand gel without breaking, it can absorb seismic load and suppress the increase in excess pore water pressure to suppress liquefaction.

  In the present invention, by mixing bubbles in a low-concentration silica solution, the bubbles are slid while deforming between soil particles without causing clogging between the soil particles while the bubbles are mixed, rather than injecting the bubble aqueous solution itself. Then, it permeates into the ground extensively and gels to form a homogeneous air-mixed consolidated soil.

  A similar effect can be achieved by using a polymer material or a surfactant to facilitate the expansion of bubbles by sliding into gaps in the ground. Particularly when the silica concentration is low, mixing the polymer material can increase the viscosity of the diluted silica solution and prevent the silica solution from being dispersed and diluted in the groundwater.

  Inject inside the restraint state.

  By injecting a silica colloid or a silica solution in a non-alkaline region and a silica solution containing air bubbles as an active ingredient, the present invention uses silica gel generated around the air bubbles in the ground by reaction of silica and acid or its reactant. Regardless of the flow of the groundwater that is covered, it is possible to prevent the desaturation from being reduced because it is held in a predetermined injection region and the saturation due to the groundwater can be prevented from increasing.

  In the silica solution containing bubbles, the silica particles adhere to the contact surfaces of the soil particles, and the bubbles are taken into the silica gel between the soil particles. For this reason, the excess pore water pressure due to the seismic load is absorbed by the shrinkage of the bubbles through the silica gel, and at the same time, the skeleton structure of the soil particles is maintained by the adhesive force of the silica particles.

  As a result, since the shear stress is reduced by the shrinkage of the bubbles against the repeated shear stress caused by large earthquake motion, the soil skeletal structure can be prevented from being destroyed. Become. Further, it can withstand large earthquake motions due to the synergistic effect of the shrinkage of bubbles and the adhesive force of silica, and can exhibit high liquefaction strength even when the silica concentration is low or the degree of unsaturation is small.

  In addition, even if the bubble content is increased, the bubble-containing silica solution forms a large number of unsaturated soil blocks containing the soil particles in a block shape, and the soil particles are fixed with silica gel. The degree of saturation increases and a high liquefaction strength can be expected.

  This is a gel that has a low silica concentration and does not cause fracture strain, so that a sufficient liquefaction strength can be obtained even when the silica concentration is low, and an excellent ground improvement effect can be obtained.

  In this case, the low-concentration silica gel present in the gap between the soil particles deforms and follows the load without breaking. For this reason, it is considered that the gel existing between the soil particles deforms without breaking and acts on the bubbles to contract the volume of the bubbles and absorb the seismic load due to the shear stress of a large earthquake.

  The ground improvement method of the present invention is characterized by containing air bubbles in the injection material, and by generating air bubbles in combination with an air generator or a microbubble generator, if necessary, Saturation can be adjusted. In this case, the air amount may be set from the gas amount corresponding to the target degree of unsaturation.

  Further, by injecting an aqueous solution containing an electrolyte such as a silica solution, an alkali, an acid, or a salt and a bubble mixture, the duration of bubbles in the ground can be extended and the permeation range can be expanded.

  Furthermore, the ground can also be desaturated by setting the target degree of unsaturation in a predetermined improvement region, setting the amount of gas required, and forming bubbles in the ground.

  As a result of research by the present inventors, it has been found that the present invention has the following characteristics.

  In the present invention, the bubble means air, but carbon dioxide and air containing carbon dioxide can also be included. Carbon dioxide has the effect of reacting with alkali of water glass or colloidal silica to precipitate silica and improve the durability of silica gel. Therefore, when air bubbles are further added to the carbon dioxide solution to which silica is added, the air bubbles are fixed between the soil particles in the ground by the silica gel, thereby further improving the liquefaction strength. .

In order to lower the degree of saturation of the ground, it is necessary to generate an amount of gas corresponding to the degree of unsaturation in the ground. The relationship between the volume of gas and the pressure when carbon dioxide is used as an example of gas is shown. Carbon dioxide is soluble. The amount of carbon dioxide dissolved in the aqueous solution (gas volume) is affected by temperature and pressure. The graph shown in FIG. 20 shows the carbon dioxide absorption coefficient (relation between the pressure and the amount of dissolved carbon dioxide).

  From the graph, 1.745L of carbon dioxide dissolves per liter of groundwater in the ground at 20 ° C where the upper pressure is 100kPa.

Volume (L) = Volume of water (L) x GV = 1 x 1.745 = 1.745L
In a tank under a pressure of 400 kPa at 20 ° C, 4.388 L of carbon dioxide dissolves per liter of water.

Volume (L) = Volume of water (L) x GV = 1 x 4.388 = 4.388L
The carbon dioxide dissolved in the injection material in the sealed and pressurized container penetrates into the ground, so that the pressure decreases and the dissolved carbon dioxide gasifies, so that the target degree of unsaturation can be adjusted. it can.

  The inventor further provides a method for injecting a bubbled silica solution. That is, the present invention was completed by finding the following characteristics.

  (1) A solidified part is formed by gelation of a silica solution or a bubble-containing silica solution in a predetermined ground improvement region, or a solidified wall is formed so as to surround the injection region, and a region between the solidified bodies. The bubble mixture is injected into the tube to develop a liquefaction prevention function.

  (2) By reducing the silica concentration, the silica gel that surrounds the bubbles adapts without breaking to the pressure of the bubbles, or adapts without breaking when an earthquake load is applied, causing the bubbles to contract and excess gaps. Absorbs water pressure. For this reason, a synergistic effect is obtained in which the liquefaction strength is greater than the liquefaction strength when the silica solution or the bubble solution is used alone.

  (3) By reducing the silica concentration, the gelled product of the bubble-containing silica solution has a very small amount of reaction product and the pH of the solidified body can be almost neutral. Excellent environmental conservation for structures.

  The present invention provides a liquefaction preventive work that eliminates the disadvantages of the liquefaction countermeasure work caused by the mixed injection of the above chemical solution and air bubbles by using a silica solution and air bubbles in combination.

  In addition, the groundwater advancing in the ground directly under the structure by combining the method of creating a constraining wall directly under the structure or the outer periphery of the structure or directly under the structure and the method of desaturating the ground in the area with the bubble mixture. By preventing the liquefaction, an unsaturated ground is formed on the foundation base plate of the structure to prevent liquefaction.

  The water-impervious wall can be formed by improving the ground of the outer peripheral ground of the structure by injecting grout with excellent durability, press-fitting a plastic gel, or consolidation including cement. In addition, in order to desaturate the direct base plate of the structure, water containing bubbles or liquid containing bubbles in a silica chemical injection material (high-concentration dissolved air (microvalve water) containing 10 to 100 µm bubbles) There is a method of injecting into the ground.

  (4) By installing the pile body in the ground improvement region into which the bubble-containing silica solution (silica bubble) is injected, it is possible to reduce the seismic motion acting on the pile body and improve the bearing capacity of the large pile body.

  The pile body can be formed by driving a steel pipe having an injection port into the ground and injecting cement liquid into the steel pipe from the injection port.

  Moreover, the construction of the pile body may be improved by injecting a gas-mixed silica solution in the periphery after the pile body is installed in the ground in advance. Furthermore, a plurality of pile bodies can be constructed to form a group pile.

  According to the present invention, by injecting a chemical solution mixed with microbubbles (fine bubbles) under pressure into the ground, it can be widely and evenly injected while maintaining a high concentration of dissolved gas in the ground. Because of this, microbubbles are permanently present in the ground, resulting in a high quality improvement effect, high permeability to fine-grained soil, and the ability to prevent liquefaction can be sustained over a long period of time. It is suitable for liquefaction countermeasures in areas where the ground is loosely accumulated, such as coastal landfills.

  In addition, silica gel can be added to reduce the excess pore water pressure while maintaining the skeletal structure of the soil particles at the time of earthquake by silica gel, and to prevent the reduction of unsaturation due to the flow of groundwater during the period before the earthquake occurs. Therefore, saturation due to groundwater can be prevented.

  In addition, a water-impervious wall that continues to the impervious layer on the outer periphery of the structure is created, and the ground floor directly under the structure is desaturated to prevent the transfer of groundwater directly under the structure. The liquefaction of the direct base board can be prevented.

1 shows an embodiment of a ground improvement method and a ground improvement device by unsaturation of the ground of the present invention, FIG. (A) is a schematic diagram showing the whole, FIG. (B) is a longitudinal sectional view of a bubble generating device, FIG. ), (D) are cross-sectional views taken along the line II in FIG. 1 (b). FIG. 2 shows another embodiment of the ground improvement method and ground improvement device by the desaturation of the ground of the present invention, FIG. (A) is a schematic diagram showing the whole, FIG. (B) is a longitudinal sectional view of the bubble generator, FIG. 2C is an end view taken along the line II in FIG. 1 shows an embodiment of a ground improvement method and a ground improvement device by unsaturation of the ground of the present invention, FIG. (A) is a schematic diagram showing the whole, FIG. (B) is a longitudinal sectional view of a bubble generating device, FIG. ) Is an end view taken along the line II in FIG. FIGS. (A) and (b) are schematic views showing an embodiment of the ground improvement method and ground improvement device by the desaturation of the ground according to the present invention. FIGS. 4A and 4B are partial longitudinal sectional views of the injection tube shown in FIG. FIG. 5 shows a bubble generating device installed in the injection pipe shown in FIG. 5, where FIG. 5 (a) is an enlarged view of the portion B in FIG. 5 (b), and FIG. (C) is sectional drawing which shows the modification of a bubble generator. FIG. 2 shows another embodiment of the ground improvement method and ground improvement device of the present invention, in which FIGS. (A) and (b) are partial longitudinal sectional views of the injection pipe, and FIG. (C) is in FIGS. FIG. 3 is an enlarged sectional view of a part C, and is a longitudinal sectional view of a bubble generating device. FIG. 2 shows another embodiment of the ground improvement method and ground improvement device by the desaturation of the ground according to the present invention, FIG. (A) is a schematic view showing the whole, and FIG. (B) is a longitudinal sectional view showing a tip portion of an injection pipe. It is. FIG. 2 shows another embodiment of the ground improvement method and ground improvement device by the desaturation of the ground according to the present invention, FIG. (A) is a schematic view showing the whole, and FIG. (B) is a longitudinal sectional view showing a tip portion of an injection pipe. It is. FIG. 2 shows another embodiment of the ground improvement method and ground improvement device by the desaturation of the ground according to the present invention, FIG. (A) is a schematic view showing the whole, and FIG. (B) is a longitudinal sectional view showing a tip portion of an injection pipe. It is. FIG. 2 shows another embodiment of the ground improvement method and ground improvement device by desaturation of the ground according to the present invention, FIG. (A) is a schematic diagram showing the whole, and FIG. (B) is a longitudinal sectional view of the bubble generating device. Other embodiment of the ground improvement construction method and ground improvement device by the desaturation of the ground of the present invention is shown, and FIGS. (A) and (b) are schematic diagrams showing the whole. It is the schematic which shows other embodiment of the ground improvement construction method and the ground improvement apparatus by the desaturation of the ground of this invention, and shows the whole. FIG. 2 shows another embodiment of the ground improvement method and ground improvement device by the desaturation of the ground of the present invention, FIG. (A) is a schematic diagram showing the whole, and FIG. (B) is a partially enlarged sectional view of an injection pipe. . FIG. 2 shows another embodiment of the ground improvement method and ground improvement device by the desaturation of the ground of the present invention, FIG. (A) is a schematic diagram showing the whole, and FIG. (B) is a partially enlarged sectional view of an injection pipe. . FIGS. (A) and (b) are longitudinal sectional views showing modifications of the microbubble generator. FIG. 2 shows another embodiment of the ground improvement method and ground improvement device by the desaturation of the ground of the present invention, FIGS. (A) and (b) are schematic diagrams showing the whole, and FIG. (C) is an example of a bubble generating device. It is a schematic front view shown. Figures (a) and (b) show the ground improvement method directly under the existing structure, and are longitudinal sectional views of the improved ground. Figures (a) and (b) show the ground improvement method directly under the existing structure and are plan views of the improved ground. Figures (a) and (b) show the ground improvement method directly under the existing structure and are plan views of the improved ground. It is a graph which shows a carbon dioxide absorption coefficient (relationship between a pressure and the dissolved amount of a carbon dioxide).

  1 (a) to 1 (d) show an embodiment of a ground improvement method and a ground improvement device according to the present invention. In the figure, reference numeral 1 denotes a silica solution mixed with microbubbles (hereinafter referred to as microbubbles). This is a tank for generating “silica bubbles”, and a microbubble generator 2 is installed in the tank 1.

  Reference numeral 3 denotes a raw material liquid blending mixer for blending the raw material liquid of the silica solution fed into the tank 1 through the liquid feeding pipe 4, and reference numeral 5 denotes the tank 1 and the bubble generator 2 for the silica solution in the tank 1. Is a solution circulation pump (chemical solution circulation pump) that circulates between the two through a liquid feeding pipe 6.

  Reference numeral 7 denotes an air compressor that sends compressed air into the tank 1 to pressurize the tank 1 and sends air to the bubble generator 2. Reference numeral 8 denotes an injection pipe for the silica bubbles generated in the tank 1 into the ground. The injection pump for injecting through 9 and the reference numeral 10 are connected to the microbubble generator 2, the mixer 3, the silica solution circulation pump 5 and the injection pump 8 through signal cables 11, respectively, It is a controller to control.

  As shown in FIGS. 1B and 1C, the bubble generator 2 is in contact with a conical solution introduction path 12 having an inner diameter that gradually decreases from the lower end toward the upper end, and immediately above the solution introduction path 12. A solution discharge path 13 having a cylindrical shape is provided.

  The lower end of the solution introduction path 12 is connected to a liquid feeding pipe 6 extending from the solution circulation pump 5, and the upper end communicates with the solution discharge path 13 through the solution introduction hole 14.

  The inner diameter of the solution discharge path 13 is formed to be at least larger than the inner diameter of the upper end portion of the solution introduction path 12, and the upper end portion is greatly opened in the tank 1.

  Further, an air discharge port 15 is formed in the inner wall portion of the solution introduction hole 14, and the air discharge port 15 is connected to an air pipe 16 extending from the air compressor 7.

  In such a configuration, the solution circulation pump 5 operates, the silica solution in the tank 1 circulates between the tank 1 and the bubble generator 2 via the liquid feeding pipe 6, and the air compressor 7 operates at the same time. By discharging air from the air discharge port 15 into the solution introduction hole 14, silica bubbles are generated and discharged from the upper end of the solution discharge path 13 into the tank 1.

  In this case, the silica solution is pumped into the solution introduction path 12 via the liquid feeding pipe 6, thereby forming a swirling flow of the silica solution in the solution introduction path 12.

  Then, the silica solution flows in the direction of the solution introduction hole 14 while turning in the solution introduction path 12 along the inner peripheral surface thereof, and flows into the solution discharge path 13 through the solution introduction hole 14. In FIGS. 1 (b) and 1 (c), the arrows indicate the swirling flow of the silica solution.

  Further, a swirling flow of the silica solution is formed in the solution discharge path 13, whereby a negative pressure portion is formed in the vicinity of the central axis of the solution discharge path 13, and this negative pressure causes the solution introduction hole 14 from the air discharge port 15. Air is discharged inside.

  As shown in FIG. 1 (d), the solution introduction path is connected by connecting a liquid feed pipe 6 for pumping the silica solution to the solution introduction path 12 in the tangential direction of the inner peripheral surface of the solution introduction path 12. The swirling flow of the silica solution in 12 can be reliably formed by the flow of the silica solution.

  The air discharged into the solution discharge passage 13 flows in the vicinity of the central axis of the solution discharge passage 13 having the lowest pressure in the direction toward the opening end (upward) of the solution discharge passage 13, and passes through the thin string-like swirling gas cavity α. Form. In the solution discharge path 13, a swirling gas / liquid mixture flow β composed of a silica solution and air is formed together with the swirling gas cavity α between the solution introduction hole 14 and the tip of the solution discharge path 13.

  This swirling gas-liquid mixture flow is reduced in diameter and then tapered to be cut to generate microbubbles, and then flows while swirling greatly toward the tip of the solution discharge path 13, It is discharged into the tank 1 from the open end.

  When the swirling gas / liquid mixture flow β swirls in this way, centrifugal force and centripetal force simultaneously act on the silica solution due to the difference in specific gravity between the silica solution and air.

  For this reason, the air continues in a string shape to the vicinity of the tip of the solution discharge path 13 in the central axis in the solution discharge path 13, and is continuously cut by the occurrence of a large difference in swirling speed before and after the vicinity of the tip of the solution discharge path 13. Therefore, a large amount of microbubbles are generated near the end of the solution discharge path 13 and discharged into the tank 1.

  The silica solution (silica bubble) mixed with the bubbles thus generated is sent to the injection pipe 9 through the pressure feed pipe 17 when the injection pump 8 is operated, and then into the ground through the injection pipe 9. Injected into.

  2 (a) to 2 (c) show another embodiment of the ground improvement method and ground improvement device of the present invention. A silica solution introduction pipe 18 extending in the vertical direction is installed in the tank 1, and the silica solution introduction is shown. A plurality of bubble generating devices 2 are installed on the side of the pipe 18 at regular intervals in the pipe axis direction of the introduction pipe 18.

  Each bubble generating device 2 is installed perpendicularly (horizontally) to the tube axis direction (vertical direction) of the silica solution introduction tube 18, whereby the solution introduction path 12, the solution introduction hole 14, and the solution discharge path of each device 2. 13 are arranged adjacent to each other in order from the silica solution introduction pipe 18 toward the tip of the bubble generating device 2, and the solution introduction path 12, the solution introduction hole 14, the solution discharge path 13 and the silica solution introduction pipe 18 communicate with each other. Yes.

  An air discharge port 15 is formed in the inner wall portion of the solution introduction hole 14, and an air pipe 16 extending from the air compressor 7 is connected to the air discharge port 15.

  Other configurations are substantially the same as those of the embodiment described with reference to FIGS. Further, according to the same principle as that of the embodiment described in FIGS. 1A to 1C, microbubbles are generated in the vicinity of the end of the solution discharge path 13 of each bubble generating device 2, and thereby silica bubbles are efficiently used. Is generated and discharged into the tank 1. In FIGS. 2B and 2C, the arrows indicate the swirling flow of the silica solution.

  3 (a) to 3 (c) also show other embodiments of the present invention. In the embodiment described with reference to FIGS. 2 (a) to 2 (c), the solution introduction pipe 18 has an inner peripheral surface of the tank 1 in particular. A plurality of bubble generators 2 are installed on the side wall of the solution introduction tube 18 at regular intervals in the tube axis direction of the solution introduction tube 18.

  Other configurations are almost the same as those of the embodiment described with reference to FIG. 2, and the open end of the solution discharge path 13 of each bubble generating device 2 is based on the principle described in the embodiments of FIGS. 1 (a) to 1 (c). Silica bubbles are generated and discharged from the tank into the tank 1.

  According to the embodiment illustrated in FIG. 2 and FIG. 3, by providing a plurality of bubble generators 2, a large-capacity silica solution (silica bubbles) mixed with microbubbles can be generated extremely efficiently. Can do.

  4 (a) to 6 show another embodiment of the ground improvement device and the ground injection method of the present invention, which includes an injection pipe 19 for injecting silica bubbles into the ground, and the injection pipe 19 is an outer pipe 20. And an inner tube 21 installed in the outer tube 20.

  A drill bit 20a and a drill water outlet 20b are provided at the lower end of the outer tube 20, and a cap 22 is movably attached to the lower end of the inner tube 21. A plurality of bubble generating devices 2 are installed at regular intervals in the tube axis direction in the gap between the outer tube 20 and the inner tube 21.

  As shown in FIG. 6 (a), each bubble generating device 2 is in contact with the conical solution introduction path 12 that gradually decreases in diameter from the inner pipe 22 side toward the outer pipe 21 and the solution introduction path 12, and has a cylindrical shape. A solution discharge path 13 is provided.

  The solution introduction path 12 communicates with the inner pipe 21, and also communicates with the solution discharge path 13 through the solution introduction hole 14, and the solution discharge path 13 penetrates the side wall of the outer pipe 20 and is largely outside the outer pipe 20. It is open.

  An air discharge port 15 is formed in the inner wall portion of the solution introduction hole 14, and an air pipe 16 extending from the air compressor 7 is connected to the air discharge port 15.

  Next, a method for injecting silica bubbles by the ground improvement device in such a configuration will be described.

  (1) First, the injection tube 19 is rotated while discharging the drilling water from the drilling water discharge port 20b at the tip, and the injection tube 19 is inserted into the ground by drilling with the drilling bid 20a.

  Since the lower end portion of the inner tube 21 is blocked by the cap 22, the drilling water does not flow into the inner tube 21 and is not ejected to the ground while the injection tube 19 is inserted into the ground.

  Further, by inserting a cone 23 made of a piece of wood, rubber, resin or the like into the solution discharge path 13, no excavated soil flows into the solution discharge path 13. Further, when the silica bubbles are injected into the ground, the cone 23 can be removed by blowing off with the discharge pressure of the silica bubbles.

  (2) Next, silica bubbles are injected into the ground through the injection tube 19. Specifically, a silica solution is injected into the inner tube 21 from the ground. At the same time, the air compressor 7 is operated to send air into each bubble generating device 2 via the air pipe 16.

  Then, the silica solution in the inner tube 21 flows into the solution discharge path 13 through the solution introduction path 12 and the solution introduction hole 14 of each bubble generator 2. At the same time, air flows from the air discharge port 15 into the solution introduction hole 14.

  Then, according to the principle explained in the embodiment of FIGS. 1 (a) to 1 (c), silica bubbles composed of silica solution and air are discharged from the opening end of the solution discharge path 13 of each bubble generator 2 into the ground. The ground is desaturated.

  Even if the cap 22 attached to the tip of the inner tube 21 is pushed downward by the injection pressure of the silica solution, the lower end portion of the inner tube 21 is closed by the cap 22, so that the silica solution There is no escape from the drilling water outlet 20a.

  FIG. 6 (c) shows a modification of the bubble generating device 2, in which a solution introduction path 12 and a solution discharge path 13 are formed adjacent to each other in the vertical direction. The other configuration and the principle in which silica bubbles are generated and discharged into the ground are substantially the same as those in the embodiment described in FIGS. 6 (a) and 6 (b).

  In particular, in the embodiment shown in FIG. 4B, a branch valve (electromagnetic valve) 46 is connected to each of the pressure feeding pipes 17 extending from the bubble generating device 2 to each of the plurality of injection pipes 19, and each electromagnetic valve 46 is connected to the centralized management device 47 via the signal cable 11, and opening / closing is controlled by the centralized management device 47.

  As a result, each electromagnetic valve 46 has a valve or a plurality of valves, or all the valves are sequentially or simultaneously opened, or selectively opened or closed to open or close silica bubbles in the plurality of injection pipes 19 in order or simultaneously. Any choice can be made. Thus, silica bubbles can be injected into the injection tube 19 according to the injection situation.

  7 (a) to (c) show another embodiment of the ground improvement method and ground improvement device of the present invention, which includes an injection pipe 24 for injecting silica bubbles into the ground, and the injection pipe 24 is an outer pipe 25. The outer tube 25 is provided with an outer tube discharge port 25a at a different position in the tube axis direction, and a check valve 27 made of a rubber sleeve or the like is attached to the outer tube discharge port 25a.

  In particular, the outer tube packer 28 is attached to the outer tube 25 in the embodiment shown in FIG. 7B at different positions in the tube axis direction. The outer tube packer 28 is attached at a position where one or more outer tube discharge ports 25a adjacent to the tube axis direction of the outer tube 25 are vertically sandwiched, and each outer tube packer 28 is an outer tube provided on the side wall of the outer tube 25. It communicates with the inside of the outer tube 25 through the tube packer discharge port 25b.

  The inner pipe 26 includes an inner pipe discharge port 26a and an inner pipe packer 29 at a plurality of positions different in the pipe axis direction. The inner pipe packer 29 includes one or more inner pipe discharge ports 26a adjacent to the inner pipe 26 in the pipe axis direction. Each of the inner tube packers 29 communicates with the inner tube 26 via an inner tube packer outlet 26b provided on the side wall of the inner tube 26.

  The outer tube packer 28 and the inner tube packer 29 are formed from an inflatable bag such as rubber, and the inner tube discharge port 26a is formed to have a smaller diameter than the inner tube packer discharge port 26a. The opening area of 26a is formed to be smaller than the inner cross-sectional area (inner pipe flow path) of the inner pipe 26.

  The bubble generator 2 is incorporated in the upper end portion of the inner tube 26. The bubble generating device 2 includes a conical solution introduction path 12 having an inner diameter that gradually decreases in the downward direction of the inner tube 26, and a solution discharge path 13 that is in contact with the solution introduction path 12 and has a cylindrical shape. The inner diameters of the upper end portion of the solution introduction path 12 and the lower end portion of the solution discharge path 13 are formed to be substantially the same as the inner diameter of the inner tube 26.

  Further, an air discharge port 15 is formed in the inner wall portion of the solution introduction hole 14, and the air discharge port 15 is connected to an air pipe 16 extending from an air compressor (not shown). Note that a bubble generating device 64 shown in FIG. 17 (c) may be incorporated in the upper end portion of the inner tube 26 in place of the bubble generating device 2.

  In such a configuration, first, a method for injecting silica bubbles by the ground improvement device shown in FIG. 7 (a) will be described.

  (1) First, the outer pipe 25 of the injection pipe 24 is built into the hole drilled by boring or the like, and a low-strength seal grout 30 such as cement slurry is injected into the gap between the outer pipe 25 and the hole wall. To do.

  (2) Next, the inner pipe 26 is installed in the outer pipe 25. Then, a silica solution is injected into the inner tube 26. At the same time, air is sent from the air compressor to the bubble generator 2 through the air pipe 16.

  Then, the silica solution in the inner pipe 26 flows into the solution discharge path 13 through the solution introduction path 12 and the solution introduction hole 14. At the same time, air flows from the air discharge port 15 into the solution discharge path 13. Then, silica bubbles are generated from the opening end of the solution outlet 13 and discharged into the inner tube 26.

  The silica bubbles discharged from the opening end of the solution discharge path 13 first flow into the inner tube packers 29 via the inner tube discharge port 26a, whereby each inner tube packer 29 expands to form the outer tube 25. A columnar space 31 is formed between the inner pipe 26 and the inner pipe 26.

  Further, the silica bubble flows into the columnar space 31 through the inner tube discharge port 26a, and flows between the outer tube 25 and the hole wall from the columnar space 31 through the outer tube discharge port 25a.

  Then, the seal grout 30 is divided by the discharge pressure and penetrates into the surrounding ground, thereby unsaturating the surrounding ground.

  In the embodiment shown in FIG. 7 (b), there is no step of injecting the seal grout 30 in the step (1), and the outer tube packer is injected by injecting a filler such as cement grout into the outer tube packer 28. 28 is expanded to form a columnar space 31 between the outer tube 25 and the hole wall. In this case, the filling material is an inner pipe different from the inner pipe 26.

  In the step (2), when the silica solution is injected through the inner tube 26, the silica bubbles flow into the columnar space 31 through the inner tube discharge port 26a, and the surroundings from the columnar space (columnar permeation source) 31 Penetration into the ground of the soil and the surrounding ground becomes unsaturated.

  FIGS. 8 to 11 show other embodiments of the ground improvement method and the ground improvement device of the present invention, and according to these embodiments, silica bubbles are injected simultaneously into a plurality of injection points in a particularly soft ground. In addition, an optimal amount of silica solution can be injected for each layer having different ground conditions. Further, the injection material can be injected, interrupted, resumed, or continued simultaneously at a plurality of injection points or by selecting one or a plurality of injection points.

  To explain in order, the ground improvement method and the ground improvement device shown in FIGS. 8 (a) and 8 (b) are a pressurized tank 1 for generating silica bubbles, a bubble generating device 2, a raw material liquid compounding kisa 3, a silica solution. A circulation pump 5, an air compressor 7, an injection pump and an injection pipe 9 are provided, all of which are substantially the same as those described in the embodiment shown in FIGS. 1 (a) to (d). . In particular, a plurality of injection pipes 9 are provided, and each injection pipe 9 is embedded at a plurality of points and connected to the pressurized tank 1 via a pressure feed pipe 17.

  The injection tube 9 is an injection tube used in an injection method such as a double packer method or an extractor method, and each pumping tube 17 between each injection tube 9 and the tank 1 is a bubble generator 32 and a pressure / flow meter. 33 are connected to each other.

  FIG. 8 (b) shows an injection pipe used in the double packer method, which has a plurality of outer pipe discharge ports 9b and check valves 9c at different positions in the pipe axis direction of the outer pipe 9a, An inner tube discharge port 9e and double packers 9f and 9f are attached to the tip of 9d.

  The bubble generating device 32 is a device for regenerating the myo bubbles when the silica bubbles generated in the tank 1 are sent to the injection pipes 9. For example, a bubble generating device as shown in FIG. It is connected.

  The pressure / flow meter 33 is a device for pumping an optimal amount of silica bubbles for each layer having different ground conditions at each injection point.

  The ground improvement method and ground improvement device shown in FIGS. 9 (a) and 9 (b) include a tank, a bubble generator, a raw material liquid mixer, a silica solution circulation pump, an air compressor, etc. (all not shown), In all cases, the same elements as those described in the embodiment shown in FIGS. 1 (a) to 1 (d) are arranged.

  In addition, a plurality of injection pipes 34 for injecting the silica bubbles generated in the tank 1 into the ground are provided. Each injection pipe 34 is embedded at a plurality of points on the ground and connected to the tank via the pressure feeding pipe 17. Has been. Further, a bubble generating device 32 and a pressure / flow meter 33 are connected to each pumping pipe 17.

  Each injection tube 34 includes an outer tube 35 and an inner tube 36. The outer tube 35 includes a plurality of outer tube discharge ports 35a and check valves 35b at different positions in the tube axis direction, and the inner tube 36 has an inner tube at the tip. A discharge port 36 a and a double packer 36 b are provided, and a bubble generator 37 is installed in the inner pipe 36.

  For example, the bubble generator 37 illustrated in FIG. 7C is installed in the bubble generator 37, and the air discharge port 15 of each bubble generator 37 is connected to an air pipe 16 extending from the compressor 7 on the ground.

  The ground improvement method and ground improvement device shown in FIGS. 10 (a) and 10 (b) are connected to a pressurized tank 38 for dissolving air in a silica solution under high pressure, and to the pressurized tank 38 via a pressure feed pipe 17. The silica solution in which the air in the pressurizing tank 38 is dissolved is distributed to a plurality of pipelines in an optimum amount by pressure and fed to the silica solution distributed from the distributor 39 through the branch valve 40. A bubble generator 41 for mixing microbubbles, a plurality of injection pipes 42 for injecting silica bubbles generated by each bubble generator 41 into the ground, and a pressure / flow meter 43 are provided.

  In the branch valve 40, the discharge amount of silica bubbles discharged from the respective injection pipes 42 into the ground is adjusted by adjusting the valve opening degree by an electromagnetic motor.

Each bubble generator 41 is provided with a bubble generator (FIG. 10B) as shown in FIG. 7C, for example. The injection tube 42 is an injection tube used in a double packer method, an extractor method or the like.

  FIGS. 11 (a) and 11 (b) show another ground improvement method and ground improvement device of the present invention, a silica bubble generating device 44 for generating silica bubbles (silica solution mixed with microbubbles), and the generation of the silica bubbles. The apparatus 44 is provided with a pumping pump 45 for pumping silica bubbles to a plurality of injection points via a pumping pipe 17, and a plurality of injection pipes 42 for injecting silica bubbles at each injection point.

  The silica bubble generating device 44 includes a tank 1, a bubble generating device 2, a raw material liquid blending mixer 3, a solution circulation pump 5, an air compressor 7, and the like, all of which are the embodiments of FIGS. 1 (a) to 1 (d). Almost the same as described in FIG. 11 is arranged (FIG. 11 (b)).

  The injection pipes 42 are embedded at a plurality of points, and each injection pipe 42 is connected to the tank 1 via the pressure feeding pipe 17. Further, as the injection tube 42, an injection tube (FIGS. 5, 7, 8, 9, 12, and 13 to 16) such as a double packer or an extractor is used. A bubble generating device 32 and a pressure / flow meter 33 are connected to the pressure feeding pipe 17 between the ones.

  The bubble generating device 32 is a device for regenerating the myo bubbles when the silica bubbles generated in the tank 1 are sent to the injection pipes 42 via the pressure feeding pipes 17, for example, as shown in FIG. 7 (c). A bubble generator is connected.

  The pressure / flow meter 33 is a device for pumping an optimal amount of silica bubbles according to the ground conditions that are different for each layer at each injection point.

  In addition, an electromagnetic valve that opens and closes the flow path of the injection material to the plurality of injection pipes 42 or a branch valve 46 for arbitrarily adjusting the distribution amount of the injection material is connected to the pressure feeding pipe 17, and in particular, the branch valve Is configured so that its opening degree can be electromagnetically adjusted.

  Further, the valve generator 32 is configured to be able to arbitrarily supply air sent from the compressor 7. These are collectively managed by the centralized management device 47.

  FIGS. 12 and 13 also show another embodiment of the ground improvement method and ground improvement device of the present invention, and in particular, silica bubbles can be injected simultaneously or selectively into a plurality of injection points of soft ground. In addition, an optimum amount of silica bubbles can be injected into each layer having different ground conditions, and the start, stop, restart, etc. of silica bubble injection at each injection point can be arbitrarily controlled.

  12 (a) and 12 (b), the ground improvement method and the ground improvement device are operated by an independent drive source 48 and controlled by a centralized management device 47, and a plurality of unit pumps 49 are provided. A plurality of infusion pipes 42 connected to the unit pump 49 via the pressure feeding pipe 17, and a bubble generating device 41 connected to each of the pressure feeding pipes 17 disposed between the unit pump 49 and the infusion pipe 42, and bubble generation The device 41 is provided with a bubble generator as shown in FIG. 7 (c).

  Then, the silica solution is generated into silica bubbles in the bubble generator 41 by the operation of each unit pump 49, and is pumped to the injection pipe 42 at each injection point via the pressure feed pipe 17, and each injection point is connected via the injection pipe 42. Injected into the ground. Further, the unit pump 49 is controlled by the centralized management device 47 so that the start, stop, restart, etc. of silica bubble injection at each injection point can be arbitrarily controlled.

  The ground improvement method and the ground improvement apparatus shown in FIG. 13 include a plurality of injection pipes 42 for injecting silica bubbles into the ground at each injection point, a plurality of pressure feeding pipes 17 for connecting the injection pipes 42 to each other, and silica Silica bubble generator 41 that mixes microbubbles into the solution to generate silica bubbles, and pumps silica bubbles to each injection point via pressure feed pipe 17, and into the ground at each injection point via injection pipe 42 A plurality of unit pumps 49 for injecting silica bubbles, a flow path switching valve 50 for switching the flow path of silica bubbles at each injection point, and a pressure / flow meter 43 for measuring the flow rate and / or pressure of silica bubbles at each injection point And a centralized management device 47 for controlling the unit pump 49 and the pressure / flow meter 43, and a centralized monitoring device 51 for monitoring the injection state of silica bubbles at each injection point.

  Then, while monitoring the injection pipe 42, the pressure / flow meter 43, the silica bubble generator 44 and the unit pump 49 at each injection point in the central monitoring device 51, each injection is performed by controlling these devices in the central management device 47. It is configured so that the injection, stop, restart, etc. of silica bubbles at the point can be arbitrarily controlled.

  FIGS. 14 and 15 also show another embodiment of the ground improvement method and ground improvement device of the present invention, in which silica bubbles can be injected simultaneously or selectively into a plurality of injection points of soft ground, and In addition, it is possible to inject an optimal amount of silica bubbles for each layer having different ground conditions, and further to carry out coarse filling prior to injection of silica bubbles, it is possible to prevent the escape of silica bubbles.

  The ground improvement method and ground improvement device shown in FIGS. 14 (a) and 14 (b) are provided with a plurality of injection pipes 42 for injecting silica bubbles into the ground, and each injection pipe 42 is inserted into a drilling hole 52. An outer tube 53 and an inner tube 54 inserted into the outer tube 53 are provided.

  A plurality of primary injection material discharge ports 53a are formed at different positions in the tube axis direction of each outer tube 53, and a plurality of secondary injection material discharge ports 53b are formed between the primary injection material discharge ports 53a and 53a.

  In addition, outer tube packers 55 and 55 each comprising an inflatable bag are attached to the upper and lower sides of each primary injection material discharge port 53a. Further, a columnar space water guide member 56 is attached to the outer periphery of the secondary injection material discharge port 53b between the outer tube packers 55 and 55 so as to cover the outer periphery of the outer tube 53 including the secondary injection material discharge port 53b.

  As the inner tube 54, an injection inner tube used in the double packer method, the extractor method or the like is used, and as shown in FIG. 14 (b), double packers 54a, 54a and one or a plurality of inner tubes are formed at the tip. A discharge port 54b is provided.

  A bubble generating device 41 is installed at the upper end of the inner tube 54. As the bubble generating device 41, a bubble generating device as shown in FIG. 7 (c) is used.

  In such a configuration, a method of injecting silica bubbles will be described.

  (1) First, the outer tube 53 is inserted into the hole 52, and an injection inner tube (not shown) different from the inner tube 54 is inserted into the outer tube 53. Then, a solidified material such as air or mortar is injected into each outer tube packer 55 through the injection tube to expand the outer tube packers 55 and 55, thereby causing the hole wall of the drilling hole 52 and the upper and lower sides of the outer tube 53 to rise and fall. An injection material penetration source is formed between the tube packers 55 and 55.

  (2) Next, an injection pipe (not shown) different from the inner pipe 54 is inserted into the outer pipe 53, and through the injection pipe, from the primary injection material discharge port 53a of the outer pipe 53 into the surrounding ground. Inject injectable or suspending injection material. This step is so-called rough filling injection, and is performed to prevent the silica bubbles from being discharged prior to the injection of the silica bubbles.

  (3) Next, the inner tube 54 is inserted into the outer tube 53 and a silica solution is injected into the inner tube 54. Then, the silica solution in the inner tube 54 is generated into silica bubbles in the silica bubble generator 41.

  The generated silica bubbles are discharged from the secondary injection material discharge port 53b of the outer tube 53 through the discharge port 54b of the inner tube 54 and between the double packers 54a, 54a between the outer tube 53 and the inner tube 54. It flows into the inside and penetrates into the surrounding ground from the columnar space water conveyance member 56, and the surrounding ground is desaturated.

  The ground improvement device shown in FIGS. 15 (a) and 15 (b) includes a plurality of injection pipes 42 for injecting silica bubbles into the ground, and each injection pipe 42 and an outer pipe 57 inserted into a drilling hole 52. An inner tube 58 inserted in the outer tube 57 is provided.

  A plurality of primary injection material discharge ports 57a are formed at different positions in the tube axis direction of the respective outer tubes 57, and a plurality of secondary injection material discharge ports 57b are formed between the primary injection material discharge ports 57a and 57a.

  Note that the interval between the primary injection material discharge ports 57a and 57a adjacent to each other in the tube axis direction of the outer tube 57 is wide, and a plurality of secondary injection material discharge ports 57b are formed therebetween.

  Each primary injection material discharge port 57a and secondary injection material discharge port 57b is provided with a check valve 59 made of a rubber sleeve or the like, and further, at a position having the secondary injection material discharge port 57b of the outer tube 57. A columnar space water guiding member 60 is attached so as to cover the secondary injection material discharge port 57b.

  The inner pipe 58 is an injection pipe used in a double packer method, an extractor method or the like, and a bubble generator 41 is installed at the upper end of the inner pipe 58. As the bubble generating device 41, a bubble generating device as shown in FIG.

  In such a configuration, a method of injecting silica bubbles will be described.

  (1) First, the outer tube 57 is inserted into the hole 52, and the seal grout 61 is injected between the hole wall of the hole 57 and the outer tube 57.

  (2) Next, an injection tube different from the inner tube 58 is inserted into the outer tube 57. Then, an instantaneous or suspendable injection material is injected into the surrounding ground from the primary injection material discharge port 57a of the outer tube 57 through the injection tube. This step is performed to prevent the silica bubbles from being discharged prior to the injection of the silica bubbles (coarse filling injection).

  (3) Next, the inner tube 58 is inserted into the outer tube 57 and a silica solution is injected into the inner tube 58. Then, the silica solution in the inner tube 58 is generated into silica bubbles in the silica bubble generator 41.

The generated silica bubbles flow into the columnar space water conveyance member 60 from the secondary injection material discharge port 57b of the outer tube 57 through the double packer of the outer tube 57 and the inner tube 58, and seal grout from the columnar space water conveyance member 60. It penetrates the surrounding ground through 61 and desaturates the surrounding ground.

  FIGS. 16 (a) and (b) both show a modification of the bubble generating device installed at the tip of the injection tube, and the bubble generating device shown in FIG. It is installed in the injection tube to inject.

  In addition, a conical solution introduction path 12 whose inner diameter gradually decreases in the downward direction, and a solution discharge path 13 that is in contact with the solution introduction path 12 directly below and gradually increases in diameter toward the lower end direction are provided. The solution introduction path 12 and the solution discharge path 13 communicate with each other through the solution introduction hole 14.

  An air discharge port 15 is formed in the inner wall portion of the solution introduction hole 14, and the air discharge port 15 is connected to an air pipe 16 extending from an air compressor (not shown).

  A check valve 62 is attached to the lower end of the solution discharge path 13. The check valve 62 is a valve that prevents the reverse flow of silica bubbles discharged into the ground and the inflow of groundwater, and is attached so as to always block the lower end portion of the solution discharge path 13 by the action of the compression spring 62a.

  In such a configuration, the silica solution injected into the injection tube flows from the solution introduction path 12 into the solution discharge path 13 through the solution introduction hole 14 due to the injection pressure. Further, the air is discharged from the air discharge port 15 into the solution discharge path 13.

  At that time, a swirling flow of the silica solution is formed in the solution introduction path 12 and the solution discharge path 13, and the silica solution flows in the direction of the solution introduction hole 14 while swirling along the inner peripheral surface of the solution introduction path 12, The solution flows into the solution discharge path 13 through the solution introduction hole 14.

  Further, a negative pressure portion is formed in the vicinity of the central axis of the solution discharge path 13 by the formation of the swirling flow of the silica solution, and air is sucked into the solution discharge path 13 from the air discharge port 15 by this negative pressure.

  The air discharged into the solution discharge path 13 flows in the vicinity of the central axis of the solution discharge path 13 having the lowest pressure toward the opening end of the solution discharge path 13 to form a thin string-like swirling gas cavity. Further, in the solution discharge path 13, a swirling gas-liquid mixture flow β composed of a silica solution and air is formed between the solution introduction hole 14 and the tip of the solution discharge path 13 together with the swirling gas cavity.

  The swirling gas-liquid mixture flow β is reduced in diameter and then tapered, and then cut to generate microbubbles. After that, the swirling gas-liquid mixture flow β flows while largely swirling toward the tip of the solution discharge path 13, and the check valve 62 Is spread and discharged from the end of the solution discharge path 13 into the ground.

  Also, the bubble generator shown in FIG. 16 (b) is installed in an injection pipe for injecting silica bubbles into the ground. In addition, a solution introduction path 12 having a conical shape whose inner diameter gradually becomes smaller in the lower end direction, and a solution discharge path 13 in a cylindrical shape that is in direct contact with the solution introduction path 12 are provided. The solution introduction path 12 and the solution discharge path 13 communicates with the solution introduction hole 14.

  An air discharge port 15 is formed in the inner wall portion of the solution introduction hole 14, and the air discharge port 15 is connected to an air pipe 17 extending from an air compressor (not shown).

  Further, a vortex generator 63 formed in a spiral shape in the solution discharge path 13 is installed in the axial direction of the solution discharge path 13.

  In such a configuration, the silica solution injected into the injection tube flows from the solution introduction path 12 into the solution discharge path 13 through the solution introduction hole 14 due to the injection pressure. Further, the air is discharged from the air discharge port 15 into the solution discharge path 13.

  Then, the silica solution and air merge in the solution discharge path 13 and flow toward the tip of the solution discharge path 13. Further, at that time, a swirl flow is generated in the silica solution by the vortex generator 63, whereby silica bubbles are generated according to the principle described in the embodiment of FIG. 1 and discharged from the lower end of the solution discharge path 13 into the ground. .

  FIGS. 17 (a) to 17 (c) show another embodiment of the ground improvement method and the ground improvement device of the present invention. In FIG. 1 (a), reference numeral 64 indicates that fine bubbles (micro bubbles) are mixed. A bubble generator (vortex generator) for generating a silica solution (hereinafter referred to as “silica bubble”), 65 is a solution tank for storing the silica solution fed to the bubble generator, and 66 is agitated in the bubble generator 64 An injection tube that injects the mixed and dissolved silica solution and air into the ground.

  The bubble generator 64 includes an impeller 64a that rotates at high speed by power (see FIG. 17 (c)), and is connected to a liquid feeding pipe 67 extending from the solution tank 65 and an air pipe 68 that takes in air. A pressure feed pipe 69 extending to an injection pipe 66 for injecting the silica solution and gas stirred and mixed / dissolved in the bubble generator 64 into the ground is connected. Valves 70 are respectively attached to the liquid feeding pipe 67, the air pipe 68, and the pressure feeding pipe 69.

  In such a configuration, when the impeller 64a in the bubble generating device 64 is rotated at high speed by power, the silica solution is sucked into the device 64 from the solution tank 65 through the liquid feeding pipe 67 and simultaneously through the air pipe 68. Air is sucked into the device 64.

  Then, after the silica solution and air are stirred, mixed, and dissolved in the apparatus 64 by the impeller 64a that rotates at high speed, the silica solution and the air are pumped to the injection pipe 66 through the pressure feeding pipe 69 and injected into the ground from the injection pipe 66. As a result, the ground is desaturated.

  According to this embodiment, the pressurized tank 1, the solution circulation pump 5, the compressor 7 and the like in the embodiment of FIGS. 1 to 3 are not required, and the apparatus can be greatly simplified.

  On the other hand, in FIG. 17 (b), reference numeral 64 is a bubble generator, and 65 is a solution tank. The bubble generator 64 circulates the silica solution in the solution tank 65 through the liquid feeding pipe 67 to generate microbubbles in the silica solution to generate silica bubbles.

  Further, reference numeral 71 is a raw material liquid blending mixer for blending the raw material liquid of the silica solution, 72 is a silica bubble generated in the solution tank 65 is pumped to the injection pipe 66 through the pressure feed pipe 69, and This is an injection pump that injects silica bubbles into the ground.

  In such a configuration, when the impeller 64a in the device 64 is rotated at high speed by power, the silica solution in the solution tank 65 is sucked through the liquid feeding pipe 67, and at the same time, air is introduced into the device 64 through the air pipe 68. Is sucked. Then, after the silica solution and air are agitated, mixed, and dissolved in the apparatus 64, the silica solution and air are returned to the solution tank 65 via the liquid feeding pipe 67.

  In this way, silica bubbles in the solution tank 65 are generated in the solution tank 65 by circulating the silica solution in the solution tank 65 between the solution tank 65 and the device 64 via the liquid feeding pipe 67. In addition, when the injection pump 72 is operated, the silica bubbles in the solution tank 65 are pumped to the injection pipe 66 through the pumping pipe 69, and the ground is desaturated by being injected into the ground from the injection pipe 66. The

  18 to 20 show a ground improvement method for injecting a silica solution mixed with fine bubbles (microbubbles) as a countermeasure against liquefaction, particularly for the ground directly under an existing structure.

  Generally, if enough silica solution is injected with a permanent gel to completely fill the voids in the ground, the ground will not deform and liquefaction will not occur, but a small amount of ground deformation is allowed. However, it is desirable in terms of economic design to improve the ground within a range that does not lead to large liquefaction.

  To that end, chemical injection containing bubbles is effective, but the injection material does not reach the range where there is a risk of liquefaction, or it is injected only in the periphery of the injection tube. It is necessary to solve such problems.

  The ground improvement method illustrated in FIGS. 17 to 19 is a ground improvement method of the present invention that solves such a problem, using a silica solution mixed with a silica solution and fine bubbles (microbubbles) as an injection material, By injecting both silica solution or silica solution and silica solution mixed with fine bubbles into the ground directly under and / or around the existing structure, the ground where there is a risk of liquefaction is desaturated, and part of it By solidifying, liquefaction is prevented.

  Specifically, a shield wall (continuous underground wall) 74 is created in the ground directly under the existing structure 73 on the ground so as to surround the outer periphery of the existing structure 73 as shown in FIG. Then, a silica solution mixed with fine bubbles is injected into the inside of the shielding wall 74 to prevent the advancing of groundwater in the direct base plate of the existing structure 73 and to try to prevent liquefaction by desaturating the ground. Is.

  The shielding wall 74 is formed by continuously improving the outer peripheral ground of the existing structure 73 up to the impermeable layer 75 by injecting permanent grout or pressing a plastic gel. In addition, in order to desaturate the ground in the shielding wall 74, water or silica solution mixed with fine bubbles (high-concentration air-dissolved solution containing bubbles of 10 μm to 100 μm) or low-strength permanent grout is injected into the ground. To do.

  In particular, when the ground in the shielding wall 74 surrounding the existing structure 73 is considerably wide, a grid-like partition wall 76 is provided inside the shielding wall 74 as shown in FIG. The ground in the shielding wall 74 is formed and divided into a plurality.

  Then, by injecting water or silica solution mixed with fine bubbles into each panel partitioned by the partition wall 76, the shearing force due to the seismic force is reduced by the rigidity of the shielding wall 74 and the partition wall 76, and it acts on the inside. The shearing force to be reduced can be reduced to prevent liquefaction.

  In addition, since the silica bubble has a low silica strength, even if a slight displacement occurs during an earthquake, the liquefaction can be prevented by suppressing the overall ground displacement by the grid-like partition wall 76, which is economical. The ground can be improved, and the shielding wall 74 and the partition wall 76 can prevent the microbubbles from being transferred, so that the liquefaction prevention effect by the microbubbles can be maintained for a long time.

In the embodiment shown in FIG. 20 (a), a plurality of consolidated bodies 77 are placed at a constant interval in the long side direction and the short side direction of the existing structure 73 in the ground immediately below the existing structure 73 built on the ground. In this case, by injecting a silica solution mixed with fine bubbles between the solidified bodies 77 and 77, the existing structure 73 is formed.
It is intended to prevent liquefaction by desaturating the ground immediately below and surrounding areas, and it is possible to economically improve the ground within a range that does not lead to large liquefaction even if a slight deformation of the ground is allowed. .

  The embodiment shown in FIG. 20 (b) shows an improved ground in which a pile body 78 is constructed in the ground into which silica bubbles (microbubble silica solution) are injected. Even if the pile body 78 alone cannot withstand a large earthquake force, the ground force is improved by injecting a silica solution mixed with microbubbles around the pile body 78, so that the earthquake force is reduced and the pile body 78 Can resist.

  According to the present invention, by injecting a chemical solution mixed with bubbles under pressure into the ground, the chemical solution can be widely and evenly injected while maintaining a high concentration of dissolved gas in the ground.

  Moreover, by this, fine bubbles are permanently present in the ground, and a high quality improvement effect is obtained. Furthermore, the permeability to fine-grained soil is high, and the liquefaction prevention effect can be sustained for a long time.

1 pressurized tank, 2 bubble generator (vortex generator),
3 Raw material liquid blending mixer, 4 liquid feed pipe, 5 silica solution circulation pump,
6 liquid feeding pipe, 7 air compressor, 8 infusion pump, 9 infusion pipe,
10 central control device, 11 signal cable, 12 solution introduction path,
13 Solution discharge path, 14 Solution introduction hole, 15 Air discharge port, 16 Air pipe,
17 Pressure feeding pipe, 18 Silica solution introduction pipe, 19 Injection pipe, 20 Outer pipe, 21 Inner pipe,
22 cap, 23 cone, 24 injection tube, 25 outer tube, 26 inner tube,
27 check valve, 28 outer tube packer, 29 inner tube packer,
30 seal grout, 31 columnar space, 32 bubble generator,
33 Pressure / flow meter, 34 Injection pipe, 35 Outer pipe, 36 Inner pipe,
37 Bubble generator, 38 tank, 39 distributor, 40 branch valve,
41 Bubble generator (vortex generator), 42 injection pipe, 43 pressure / flow meter,
44 Bubble generator (vortex generator), 45 pumping pump,
46 branch valve (electromagnetic valve), 47 central control device, 48 drive source,
49 unit pump, 50 flow rate switching valve, 51 central control device,
52 drilling holes, 53 outer pipe, 54 inner pipe, 55 outer pipe packer,
56 Column-shaped space water conveyance member, 57 outer pipe, 58 inner pipe, 59 check valve,
60 columnar space water conveyance member, 61 seal grout, 62 check valve,
63 Eddy current generator, bubble generator (vortex generator), 65 solution tank,
66 injection pipe, 67 liquid supply pipe, 68 air pipe, 69 pressure supply pipe, 70 valve,
71 Mixing mixer for raw material liquid, 72 injection pump, 73 existing structure,
74 Shielding wall (continuous underground wall), 75 impermeable layer, 76 partition wall, 77 consolidated body, 78 pile body.

Claims (1)

  Liquid that is fed through the liquid feeding pipe in the ground improvement device that desaturates the ground and prevents liquefaction by injecting the liquid mixed with fine bubbles into the surrounding structure of the existing structure and / or the ground directly below through the pipe. A bubble generator for mixing fine bubbles, a compressor for sending air to the bubble generator, and an injection pipe for injecting liquid mixed with the fine bubbles into the ground. The bubble generator passes through the liquid supply pipe Each of the liquid introduction path has a liquid introduction path, a liquid introduction hole, and a liquid discharge path through which the fed liquid flows while swirling, and the liquid introduction path is formed in a conical shape with a gradually decreasing diameter in the liquid flow direction. Is formed between the liquid introduction path and the liquid discharge path, and the air discharged from the air compressor is discharged to the inner wall surface of the liquid introduction hole. Soil improvement and wherein the discharge port is provided.

Images